The primary objectives are: a) to define the optimal conditions for conjugating amanitin diazobenzoylglycylglycine to anti-DNP rabbit IgG and retaining maximal hapten binding activity; a comparison of conditions for conjugation using water soluble carbodiimide (EDC) and N-hydroxy-succinimide esters (NHS) with ADGG will be made; b) to examine conjugates of ADGG and anti-DNP IgG which retain significant affinity for free hapten for their ability to inhibit the in vitro and in vivo proliferation of murine lymphocytic leukemia cells (EL-4) which have been coated with varying quantities of the hapten analog, TNP; c) to determine the fate of the amanitin versus the antibody carrier for in vitro inhibition studies with ADGG anti-DNP IgG conjugates in which the ADGG moiety has been labeled with 3H and the IgG moiety with 125I; d) to prepare and characterize conjugates of ADGG and monoclonal IgG directed against Thy 1.2 antigens to define the relative affinity and number of binding sites on EL-4 cells (Thy 1.2 positive) and other murine lymphoma lines containing little, if any, Thy 1.2 antigen, i.e. C1498 and S49; and e) to determine the capability of ADGG-anti Thy 1.2 IgG to specifically block the in vitro and in vivo proliferation of Thy 1.2 containing cells (EL-4) and Thy 1.2 deficient cells (C1498 and S49).